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Home / Codes / P0122
DTC code page

P0122: Throttle/Pedal Position Sensor/Switch A Circuit Low Input

Quick answer: The primary throttle or pedal position signal is stuck lower than the ECU expects.

Drivers also search this fault as TPS A low input, throttle position sensor low voltage, P0122 reduced power.

Severity: medium Family: powertrain Related paths: 9
Meaning

What P0122 usually means

P0122 narrows the primary throttle-position fault down to a low-biased signal. That usually means the ECU is seeing the A channel pulled toward ground, starved by a missing reference voltage, or trapped at an unrealistically low angle while the driver clearly is asking for more. In practice, this can feel like reduced power, delayed response, or a car that will barely acknowledge the pedal. It compounds the existing throttle graph well because it sits between the generic P0120 circuit fault and the more pattern-based P0121 plausibility complaint.

Fast triage

Start here before chasing parts

  • Scan first: save freeze-frame and pending codes before clearing anything.
  • Confirm the complaint: compare the stored code with current drivability symptoms.
  • Use context: trims, live data, and related codes usually narrow the fault faster than guesswork.
  • Work simplest to hardest: leaks, connectors, maintenance items, and known patterns before expensive components.
Initial checks

What to check first

  • Look at key-on throttle or pedal voltage before moving anything because a low-biased signal often shows itself immediately.
  • Check whether other 5-volt sensors are also acting irrational, which would point upstream of the throttle body.
  • Inspect the connector for moisture, green corrosion, or pulled pins.
Driving risk

Can you keep driving?

P0122 can make throttle response feel weak or inconsistent, so treat it as more than a nuisance if the vehicle is hesitating or limiting power.

Moderate urgency: This code often allows short-term driving, but the right fix usually comes faster when you diagnose it early instead of waiting for more codes.
Symptoms

Common symptoms

Likely causes

Common causes behind this code

  • Signal wire is shorted low or rubbed through to ground
  • 5-volt reference is missing or dragged down by another sensor on the same circuit
  • Primary throttle-position sensor track is failing low
  • Connector corrosion or water intrusion is biasing the signal downward
  • Poor ground integrity is collapsing the measured voltage

Cause phrases often tied to this code: signal short to ground, missing 5 volt reference, bad sensor ground, connector corrosion, sensor bias low.

Diagnostic order

Suggested workflow

  1. Measure reference voltage, ground, and the A signal at rest and through a smooth sweep.
  2. Compare the low-biased A channel to the companion channel to see whether only one track is affected.
  3. Check for a short-to-ground or another sensor dragging the shared 5-volt line down.
  4. Inspect the harness near brackets, intake tubing, and throttle-body movement points.
  5. Retest after repair to confirm the signal now rises smoothly and reduced power is gone.
Avoid guesswork

Common mistakes

  • Replacing the sensor before checking whether the 5-volt reference is missing for multiple components.
  • Ignoring moisture intrusion because the fault seems electrical only when wet.
  • Judging the signal with a code reader alone and never verifying voltage at the connector.
Repair path

Practical fix guidance

  • Correct the short, bad ground, or missing reference before replacing sensor hardware.
  • Replace the affected sensor assembly if the A signal stays low with known-good power and ground.
  • Verify proper throttle response under a controlled road test after the fix.
Vehicle context

Affected brands in this MVP

Brand hubs help broaden internal linking now and can evolve into make-specific diagnostic notes later.

Aliases and common searches

English phrases tied to P0122

Useful when the driver knows the wording but not the exact DTC yet.

  • TPS A low input
  • throttle position sensor low voltage
  • P0122 reduced power
Related search intent

Queries this page can answer naturally

  • P0122 code meaning
  • what does P0122 mean
  • throttle position sensor A circuit low input
FAQ

Quick questions about P0122

What usually makes P0122 a low-input fault?

A short to ground, missing 5-volt reference, bad ground, or a sensor track that is biased low are the most common causes.

Can another sensor cause P0122?

Yes. If several sensors share the same 5-volt line, one shorted sensor can drag the whole circuit down.

Does P0122 always mean the throttle body is bad?

No. Wiring and shared-voltage faults are common and should be checked first.